Crimped synthetic filament having special cross-sectional profile

ABSTRACT

Crimped synthetic filament characterized by having special cross-sectional profile remarkably deformed from circular or polygonal ones of the conventional synthetic filaments. Peculiarity of the profile, being provided with at least tripartite branches extending from a central portion, is defined by the relations among number of crimps, measure of the crosssectional profile, width and length of branches and areas of the cross section and of the smallest circumscribed circle. A manufacturing method characterized by using a spinneret having orifices of special profiles and definition of the ejecting position of coagulating air. Durable resilience to bending, enhanced covering effect of the filaments obtained with effective elimination of waxy touch or remarkable pill formation distinguished from conventional synthetic filaments are brought about by the invention.

limited States Patent [72] Inventors Terumichi Ono;

Tsuneo Haga; Yasuo Takagi; Kotaro Fujioka; Hiroshi Saito, all of Nagoya-shi, Japan [21] Appl. No. 741,068 [22] Filed June 28, 1968 [45] Patented Nov. 30, 1971 [73] Assignee Toray Industries, Inc.

Tokyo, Japan [32] Priorities June 30, 1967 [33] Japan [31] 42/41747;

June 30, 1967, Japan, No. 42/41748; June 30, 1967, Japan, No. 42/41754 [54} CRIMPED SYNTHETIC FILAMENT HAVING SPECIAL CROSS-SECTIONAL PROFILE 6 Claims, 14 Drawing Figs.

[52] U.S.CI 161/173, 161/177, 264/168, 264/177 5 l Int. Cl 002g 3/00 [50] Field ofSearch 161/173, 177; 264/168, 177

[56] References Cited UNITED STATES PATENTS 3.017.686 1/1962 Breen et a1 ..l.6l/X-Sec. DIG.

Primary Examiner- Robert F. Burnett Assislan! E.runiinerLinda M. Carlin AIl0rn0yS-RObeft E. Burns and Emmanuel .l. Lobato ABSTRACT: Crimped synthetic filament characterized by having special cross-sectional profile remarkably deformed from circular or polygonal ones of the conventional synthetic filaments. Peculiarity of the profile, being provided with at least tripartite branches extending from a central portion, is defined by the relations among number of crimps, measure of the cross-sectional profile, width and length of branches and areas of the cross section and of the smallest circumscribed circle.

A manufacturing method characterized by using a spinneret having orifices of special profiles and definition of the ejecting position of coagulating air.

Durable resilience to bending, enhanced covering effect of the filaments obtained with effective elimination of waxy touch or remarkable pill formation distinguished from conventional synthetic filaments are brought about by the invention.

PATENTED NOV30 l97| SHEET 2 BF 4 V IIIIJ/ILIJl/JJl/llL/II/I FINENESS OF FILAMENT IN DENIER (D) PATENTED NflV30 I971 SHEET 3 BF 4 O O O 5 2 Ac. wn=2Eo m0 EmmEDZ FINENESS OF FILAMENT IN DENIER (D) CRIMPED SYNTHETIC FILAMENT HAVING SPECIAL CROSS-SECTIONAL PROFILE The present invention relates to a crimped synthetic filament having special cross-sectional profile and a method for manufacturing the same. It is well-known that synthetic filaments having polygonal cross-sectional profile such as triangle, pentagonal, starprofile or their modified profile can be produced by the conventional melt spinning method. And it is also well-known that the above-mentioned synthetic filaments are produced by using a spinneret having orifices provided with a profile similar to the desired cross-sectional profile of the filaments.

However, even in case of the thermoplastic synthetic filaments having well-known cross-sectional profiles, a so-called waxy touch of the filaments of woven fabric and knitted fabrics made of these thermoplastic synthetic filaments still remains and it is desirable to eliminate the above-mentioned undesirable waxy touch. Further, the so-called prism effect of reflection caused by the particular structure of the polygonal cross section of a filament is observed and the metallic lustrous appearance caused by the above-mentioned prism effect of reflection degrades the appearance of woven of knitted fabric made of the synthetic filaments having a conventional polygonal cross-sectional profile. I

Recently, so-called high bulk yarns utilizing the thermoplastic property of thennoplastic synthetic fiber have been used for garments on a large scale without any exception even in case of synthetic filament having the above-mentioned polygonal cross section. However, generally, the resilience of the above-mentioned filaments are always insufficient for maintaining the bulkiness of the cloth, for example, when the cloth made of filaments having insufficient resilience is subjected to pressing, the bulky structure of the cloth can hardly be recovered completely even after removal of the pressing force. The above-mentioned bulkiness caused by the resilient property of the filament is hereinafter referred as a bulky effect. It is well known theoretically that the bulky effect of the textile fiber or cloth can be improved by enhancing the resistance of fiber or filament to a bending force. In the field of carpet, the above-mentioned theoretical conception concerning resilience" can be applied for effective improvement of the quality of the carpet.

Further, the problem of the so-called pill," which must be solved in order to expand the market for synthetic fiber or filaments, still exists even in case of the above-mentioned synthetic filaments having polygonal cross-sectional profiles.

A principal object of the present invention is to provide crimped synthetic filament or multifilaments in which a waxy touch which always is characteristic to the conventional synthetic filament and also metallic luster which is an undesirable feature of a synthetic filament having a polygonal cross-sectional profile are eliminated.

Another object of the present invention is to provide crimped synthetic filament or multifilaments having a high resilient property, consequently having an excellent bulky effeet."

A further object of the present invention is to provide crimped synthetic filament or filaments having superior properties against pilling.

Still another object of the present invention is to provide a unique method for manufacturing crimped synthetic filament or multifilaments having a special cross-sectional profile and thereby eliminating the above-mentioned drawbacks of the conventional synthetic filament.

Further features and advantages of the present invention will be apparent from the ensuing description with reference to the accompanying drawings to which the scope of the invention is in no way limited. V

FIGS. 1A, 1B, 1C, 10, IE, 1F and 16 are enlarged crosssectional views of several embodiments of the crimped synthetic filament of the present invention,

FIGS. 2 and 3 are explanatory drawings for defining the type of the cross-sectional profile of the synthetic filament of the present invention,

FIG. 4 is an explanatory drawing which illustrates the resistant force of the synthetic filament of the invention against a bending force,

FIGS. 5 and 6 are graphic drawings which illustrates the relation of the fineness of the filament in deniers to the number of crimps of the filament and the measure of the special cross section (R), according to the present invention,

FIG. 7 is a schematic side view of an apparatus for melt spinning the crimped synthetic multifilament according to the present invention,

FIG. 8 is a plan view of an embodiment of an orifice of the spinneret used for the apparatus shown in FIG. 7.

As it is clearly shown in FIGS. 1A and 16, the crimped synthetic filaments of the present invention are characterized by the special cross-sectional profile which is remarkably deformed from a circular profile.

Generally, the cross-sectional profile of the synthetic filament of the invention is provided with a special cross section similar to multileaves comprising at least three branches and the connecting portions between two adjacent branches are provided with a circular arc profile. The length of the branches are not always equal, further the arrangement of these branches is not always symmetrical with respect to the centroid of the cross section.

It is the most important factor of the present invention that the synthetic filament of the invention should be provided with the above-mentioned special cross-sectional profile together with fine curllike crimps having a similar shape. These curllike crimps of the filament can be obtained by several methods such as providing the cross section of the filament with an eccentric anisotropy of the shrinkable property of the microstructure of the filament with respect to the centroid of the cross section of the filament.

By repeated experiments and studies, it was found that the following conditions concerning the cross-sectional profile and curllike crimps of the filament must be satisfied in order to attain the above-mentioned objects of the invention. That is, it was was disclosed that, only when the following relative conditions between number of crimps per inch (N) and measure of special type of the cross-sectional profile of the filament (R), fineness of the individual filament (D) is satisfied, con the waxy touch of the synthetic filament obtained be eliminated and also the other objects of the invention can be attained.

0.606 log, R 20.1 1 l log D +0.845

The above-mentioned terminologies, number of crimps (N), measure of the special cross-sectional profile R are defined as follows:

1. Number ofcrimps per inch (N).

A specimen of crimped filament having a certain length is prepared. The number of crimps (N) is measured under a tension caused by a dead weight of IO mg./denier. Next the length of the specimen in inches (L) is measured under a tension caused by a dead weight of I00 mg./denier. Then the number of crimps per inch (N) is represented by (N/L).

2. Measure of the special cross-sectional profile (R).

Referring to FIG. 2, first a circumscribed circle 1 and an inscribed circle 2 of the enlarged cross-sectional profile of the filament of the present invention are drawn, and next the diameters of the above-mentioned circles l and 2 are measured. Then the measure of the special cross-sectional profile (R) is obtained by the ratio of the diameter of the circle 1 with respect to the diameter of the circle 2.

It is considered that, when the above-mentioned conditions are satisfied, very fine curllike crimps of the filament develop the periodically fine, rugged surface of the filament, further a very fine, roughened surface is realized by the rugged surface of the filament by the longitudinal edges caused by the special cross section of the filament, thereby the waxy touch of the filament on the skin of users can be effectively eliminated while the preferable crisp touch of the filament can be obtained. When the crimped filament of the invention is subjected to light, only diffused reflection of the light is obtained on account of the above-mentioned roughened and rugged surface of the filament. Consequently, a very gentle and nonmetallic luster of the filament can be obtained, while in case of the conventional synthetic filament having a polygonal cross section, only a very strong and metallic luster is obtained.

The bending moment of the individual filament is remarkably distinguished from that of the filament having a circular profile and similar fineness to the filament of the present invention. It is also understood that superior resilience of the synthetic filament or its woven cloth or knitted cloth can be obtained by the above-mentioned special cross-sectional profile of the filament according to the invention.

Further, as the high resilience of the filament of the present invention causes a large amount of space to be occupied by the textile material (hereinafter referred to as High bulkiness), this can be considered as one of the important factors for attaining the objects of the present invention.

As a result of further research work, it was disclosed that a more remarkable effect for attaining the object of the present invention can be achieved by satisfying the following condition with respect to the cross-sectional profile of the filament. That is, on the supposition that in a filament having multibranched cross section which is remarkably distinguished from a circular cross section, the length of the branches is represented by x, the width of the branches is represented by y, the area of the cross section of the filament is represented by X, the area of the smallest circumscribed circle (circle 1 shown in FIG. 2) is represented by Y, the above-mentioned conditions are shown as follows:

The above-mentioned factors x, y are measured by the following way, wherein x represents the sum of the length of the branches which correspond to the length from the intersection of the centerlines of the adjacent branches to the top end of the centerline of each branch and the intervening distances between the adjacent intersections. Referring to FIG. 3, the intersections are represented by 3 and 4, consequently, the length of the branches are represented by a, b, d and e, and the intervening distance between the intersections 3 and 4 is represented by c, than .\=a+b-l-c-l-d+e.

On the other hand, y is calculated by a rather simple way, that is, y=X/x, therefore, the above-mentioned factor (x/y) can be represented by x/y=x /X. Consequently, it can be concluded that the factor y represents the average width of the branches of the cross-sectional profile of the filament of the present invention.

As mentioned above, the synthetic filament satisfying the above-mentioned conditions of number of crimps (N) and cross-sectional profile (R, x/y and X/Y) has a remarkable covering property, high bulkiness caused by the larger space occupied by the branches on comparison with the conventional synthetic filaments, therefore, woven or knitted cloth having high bulkiness but light in weight, crisp touch without waxy feeling, excellent thermal retaining property and elegant nonmetallic luster can be produced by using the synthetic filaments ofthe invention.

Generally, woven or knitted fabrics made of synthetic fibers of filaments have a defective character resulting in the development of numerous pills. One idea for preventing the pill forming on such fabrics was the use of textile materials having low tenacity. This idea was based upon a theory that the main cause of the pill forming was due to the high tenacity of the material. However, it has become known that the above-mentioned conception is wrong because even when nonstretched synthetic filament having low tenacity such as l g/d is used for the woven material, numerous pills are still formed on the fabric. The tenacity of the above-mentioned nonstretched filament is very high such as more than I00 percent and the nonstretched filament is considered as durable material against repeated bending or extension. Consequently it can be considered that the use of materials having low tenacity for preventing the forming of pills is wrong.

By our laboratory tests, it was noticed that, when the product of tenacity (g/d) and the breaking elongation (percent) of the filament was at least below 100, the development of pills was prevented. It was further understood that the resilience or toughness of the filament is more important for preventing the development of pills, for example, when the minimum value of the moment of inertia of area of the cross section of the filament is at least more than 1.5 times that of an imaginery circle having the same cross-sectional area as the above-mentioned acutual filament, the development of pills of the fabric is remarkably prevented.

ln the above-mentioned illustration, the moment of inertia of area of the cross section of the filament is defined as follows. Referring to FIG. 4, the moment of inertia of area (I) of the cross section of the filament is calculated by the following formula.

A 1=f a dA where a "represent the distance from a certain point in the cross section to a line passing through the centroid 5 of the cross section and dA" designates a component or a small element of the cross section. These lines are represented by lines 6-7, 8-9, 10-11. Therefore, the minimum value ofl corresponds to the line 6-7, and the above-mentioned condition of the moment of inertia of area of the filament means that the filament satisfying the condition of the moment of inertia of area (I) has stronger resistance to the bending force in comparison with the filament of circular cross section and same fineness in denier as the filament of the present invention.

The above-mentioned conditions concerning the number of crimps (N), measure of the cross-sectional profile of the filament (R, x/y, X/Y), the product of tenacity (g/d) and the breaking elongation (percent), the moment of inertia of area (1), etc. are not only limited to a particular melt spun synthetic filament, but are also applicable to the so-called polyamide such as poly e-caproamide polyhexyldiamine adipamide, polyester such as polyethylene terephthalate, polyolefin such as polypropylene or polyethylene. However, the poly-ecaproamide filament is most favorably used for obtaining the remarkable effects of the present invention.

Manufacture of the crimped synthetic filament of the present invention is carried out by the method hereinafter described.

It is almost impossible to apply the well-known methods for manufacturing the conventional synthetic filaments having special cross-sectional profile such as a circular or polygonal one in the production of the crimped synthetic filament of the present invention. Even when a spinneret having orifices whose profile is substantially similar to the cross-sectional profile of the crimped synthetic filament of the present invention is adopted in the conventional melt-spinning method, the distinguished shape of the cross section of the filament just spun from the orifice tends to be mild one because of the surface tension imparted to the filaments during the period between extrusion from the spinneret and subsequent coagulation of the filament. Thus, in the production of the synthetic filament of the present invention, it is required to carry out coagulation of the filaments instantly after the filaments are extruded through the spinneret, in other word, to carry out coagulation of the filaments at a position as close to the spinneret as possible.

With respect to the orifices of the spinneret, the profile of the orifices must be provided, in accordance with the crosssectional profile of the filaments to be obtained, with a plurality of branches whose length f is much larger than the width g as shown in FIG. 8, and the length f should preferably range between 0.5 and 2.5 mm. while the width 8 should be smaller than one-fourth of the length f, or more preferably smaller than one-sixth of the length f. However, the width g should be larger than at least 0.07 mm. in order to avoid poor passage of the spinning solution during extrusion.

As to the polymer material used in the present invention, a polymer having higher degree of polymerization is required in order to obtain good results. In case of polye-caproamide polymer, a relative viscosity with respect to sulfuric acid higher than 2.4, more preferably higher than 2.6, is desirable.

An embodiment of the process for manufacturing the synthetic filaments of the present invention is shown in FIG. 7, wherein filaments l4 extruded through the orifices of the spinneret 12 of the melt-spinning equipment are subjected to coagulating air while passing through the coagulating chamber 13, oil is fed by a oiling roller 15 positioned downstream of the coagulating chamber 13 in the same manner as in the conventional melt-spinning process and taken up onto a package 18 at a takeup speed higher than 3,000 meters/minutes by a drive roller 16 and a takeup roller 17. v

The coagulating air is conducted into the coagulating chamber 13 through an air conduit 19 connected to an air supply source (not shown) and ejected to only one side of the advancing stream of filaments 14 as is clearly shown with arrows in the drawing. Ejection of the coagulating air must be performed at a position from 5 to 15 cm. below the outlet of the spinneret 12. In case ejection is performed at a position closer within 5 cm. to the spinneret 12, it results in frequent filament breakages due to high takeup speed. On the other hand, in case ejection is performed at a position more remote than l5 cm. from the spinneret 12, it results in poor a coagulating effect leading to the impossibility of manufacturing a filament having the above-described special cross-sectional profiles. The ejecting speed of the coagulation should range, in accordance with the number of crimp required for the filament manufactured, from to 100 meters/minutes, more preferably from l5 to 50 meters/minutes. The temperature of the coagulating air should range from to 22 C.

As described above, the takeup speed of the filament 14 must be higher than 3,000 meters/minutes in order to obtain the cross-sectional profile of the filament manufactured faithfully similar to the profile of the orifices of the spinneret 12. In combination with the above-described ejection of coagulating air, the takeup speed of the filaments plays an important role in the production of the synthetic filaments of the present invention. The upper limit of the takeup speed of the filaments should be 6,000 meters/minutes.

By subjecting the multifilament yarn thus manufactured to a steam treatment in a relaxed condition, numerous curl-shaped crimps can be developed on the multifilament yarn. By our further research work, it was disclosed that polymers mainly composed of polye-caproamide is especially suitable for the purpose of the present invention. Besides, the larger the ratio of the moment of inertia of the monofilament is with respect to that of an imaginary circle having the same cross-sectional area to the monofilament and the stronger is the ejection of the coagulating air, the larger is the number of crimps developed on the multifilament yarn produced.

The following examples are illustrative of the present invention, but are not to be construed as limiting the same.

EXAMPLE 1 Polye-caproamide having relative viscosity 1 of 2.8 with respect to sulfuric acid was fed to the spinning equipment shown in FIG. 7, extruded through the spinneret at a spinning temperature of 260 C and taken up onto a package at a takeup speed of 4,000 meters/minuts in order to obtain a multifilament yarn of 80 denier/20 filaments. The spinneret was provided with a cross-sectional profile shown in FIG. 18, each branch of the profile having the same length P of 1.25 mm. and same width Q of 0.] mm. Coagulating air maintained at a temperature of l8 C was ejected to the advancing stream of filaments at a position 5.5 cm. below the outlet of the spin neret at an ejecting speed ranging between 10 and 100 meters/minutes. After taken up onto the package, the multifilament yarn was treated with steam in a relaxed condition.

A knitted cloth of plain stitch having a weight of 140 g./m. was manufactured using the multifilament yarn thus obtained, and the functional properties of the knitted cloth thus obtained are illustrated intable l.

TABLE 1 Fineness of indi- Relative vidual amount of filaments Degree of covering No. of sample in denier R N crispness fibers 4 5. 0 31 4. 6 4 4. 5 36 3. 8 87 4 4.0 40 4. 3 4 4 6. 2 37 4. 5 74 Stufling-box type textured yarn 4 1.0 30 1. 2 92 False-twisting type textured yarn 4 1. 2 48 1.5 Edge-method type textured yarn 4 1. 5 25 07 In the table, Degree of crispness is the mean value of the results obtained by a handling test by 20 examiners. Crispness was classified from 1 to 5, wherein l is the poorest crispness and 5 is the best crispness.

The measurement of Relative amount of covering fibers" was carried out in the following manner. A cotton cord of 1 cm. diameter was covered with a braided structure using the multifilament yarn of the present invention, and the amount m of the multifilament yarn necessary for completely covering the cotton cord measured. Next, the same cotton cord was covered in the same manner using the conventional falsetwisting type textured yarn, and the amount m of the textured yarn necessary for completely covering the cotton cord was also measured. The value of Relative amount of covering fibers is given by the equation,

m /m 100 It will be clearly understood from this definition that the smaller is the value of Relative amount of covering fibers the more excellent is the covering effect of the yarn tested.

EXAMPLE 2 Polye-caproamide having relative viscosity 1; of 2.95 with respect to sulfuric acid was fed to the spinning equipment shown in FIG. 7, extruded through the spinneret at a spinning temperature of 260 and taken up onto a package at high takeup speeds. Coagulating air maintained at a temperature of 20 C was ejected onto the advancing stream of filaments at a position 6.0 cm. below the outlet of the spinneret at an ejecting speed ranging between 15 and 60 meters/minutes. After the filaments have been taken up onto the package in the form of a multifilament yam of 80 denier/20 filaments, the mul tifilament yarn was treated with steam in a relaxed condition. The resulting functional properties of the multifilament yarn thus obtained is illustrated in table 2, wherein samples NOs. 5, 6, 7, 8 and 9 are for a takeup speed of 3,800 meters/minutes and samples Nos. 10, l l and 12 are for a taking-up speed of 2,600 meters/minutes.

TABLE 2 Fineness Degree of of indiheat re- Particulars of the spinneret vidual Degree of taming filaments bulkiness property P in mm. Q in mm. in denier R N x/y X/Y in percent in percent TABLE 2 Continued Fineness Degree of of indiheat re- Particulars of the spinneret Vldual Degree of taining Sample filaments bulkiness property No. Profile P in mm. Q in mm. in denier R N x/y X/Y in percent in percent 10 Fig. 1B. 0. 5 0. 1 4 3. 18 2. 0 0. 42 180 106 11 lg. 1B 0. 3 O.1 4 1. 5 18 1. 3 0.55 120 102 12 0.7 0.1 4 2. 2 18 2.0 0.7 120 103 in the table, Degree of bulkiness was obtained in the following manner. A skein of 2 g. of the multifilament yarn obtained was prepared on a skein stand having a circumferential length of 60 cm., the skein thus prepared was loaded with a weight of l0 g. hung from one end of the skein and the width of the middle portion of the skein was measured in this loaded condition. Similar measurement was performed on a multifilament yarn manufactured by a similar manner using filaments of circular cross-sectional profile. Degree of bulkiness was given as a ratio of the former to the latter in percent.

Degree of heat retaining property" was obtained in the following manner. A woven cloth of plain weave having a struc ture of (80 X80) (192 X90) was manufactured using the multifilament yarn of the present invention. This woven cloth was wound completely around a member maintained at a constant ters/minutes. Coagulating air maintained at l7 C was ejected onto the advancing stream of filaments at a position 7.2 cm. below the outlet of the spinneret at an ejecting speed ranging between 20 and 50 meters/minutes. After the filaments have been taken up onto the package, the multifilament yarn was 5 subjected to steam treatment in a relaxed condition for the a polye-caproamide cn'mped yarn manufactured by the wellknown false-twisting treatment and made into shirts.

The shirts thus obtained was subjected to a 60 days wearing temperature and the value of Marsh IV" was obtained from test by examiners, the degree ofpill formation due to actual the measured quantity of thermal radiation through the covering woven cloth. in the same method, the value ofMarsh 1V utilization was examined after 60 days testing and the results are shown in table 4.

TABLE 4 Breaking Tenacity elongation (1/1) (T) in (E) in R n min. gJdenier percent ('I)X(E) Degree of pill formation 7.0 43 2. 3 1. 5 27 41 None after 60 days. 6. 0 38 2. 1 1. 8 33 59 Do. 5.0 32 1. 7 2.0 41 82 D0. 5. O 35 1.8 1. 9 76 D0. 4. 2 33 1. 6 2. 1 42 88 Slightly on the 50th day. 6.0 37 2.1 1. 9 32 61 None after 60 days. 5. 5 30 1. 9 1.8 30 54 Do. 4. 5 17 1. 7 2. 8 48 134 Remarkably after 30 days. 2.0 48 1. 2 3.0 42 126 Remarkably after 14 days. 1. 5 45 1.1 3. 1 43 133 Do. 4.0 36 0.3 3. 5 39 172 Do. 1.0 33 1.0 3.8 39 148 Remarkably on the 10th day. 1.9 48 1. 2 4.1 41 168 Remarkably on the 14th day. 1. 4 29 1.1 2. J 47 136 D0. 2. 2 50 1. 2 2.0 35 7O Observed after 30 days.

was obtained for a covering woven cloth made of multifilaln thetable. l designates Moment ofinertial of area" of the ment yarns composed of filaments of circular cross-sectional 45 yarn tested and l designates Moment of inertia of area" of profile. Degree of heat retaining property was given as a ratio of the fonner to the latter in percent.

EXAMPLE 3 functional properties of the multifilament yarn thus obtained is illustrated in table 3, wherein samples Nos. l3, l4, l5, l6 and I7 are for a takeup speed of 3.500 meters/minute and samples No. 18 is for a takeup speed of 2600 meters/minutes.

an imaginary circle whose cross-sectional area is similar to the effective cross-sectional area of the yarn tested.

While the invention has been described in conjunction with 50 certain embodiments, it is to be understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. An improved crimped synthetic filament having a fineness in a range from i to 25 denier, a transverse cross-sectional profile provided with at least three or more branches, dimensions of said cross-sectional profile being defined by;

TABLE 3 Fineness Degree of of indiheat re- Particulars of the spinneret vidual Degree of taining filaments bulkiness property P in mm. Q in mm. in denier R N x/y X/Y in percent in percent EXAMPLE 4 0.2 l 5 log D +l .0O01og N O.589 log D +2.30]

Polye-caproamide having relative viscosity 1; of 2.95 with respect to sulfuric acid was fed to the spinning equipment shown in FIG. 7, extruded through a spinneret having various cross-sectional profiles at a spinning temperature of 265 C and taken up onto a package in the form of a multifilament yarn of 70 denier/24 filaments at a takeup speed of 4,000 me- 0.606log R 0. l l l log D +0845 wherein D is the fineness of said filament in deniers N is the number of crimps per inch of filament length R is the measure of said cross-sectional profile. The microstructural shrinkable property of said filament being eccentrically anisotropic with respect to the centroid of said cross-sectional profile. 2. An improved crimped synthetic filament according to claim 1, further characterized by said cross-sectional profile being defined by the following equation;

x 32 Sum of length of branches of said cross-sectional profile of said filament y =Average width of said branches of said cross section of said filament X =Cross section area of said filament Y= Area of a smallest circumscribed circle of said cross section of said filament.

3. An improved crimed synthetic filament according to claim 1, further characterized by a minimum value of a moment of inertia of area of said cross section of said filament being more than 1.5 times larger than that of an imaginary circle having the same area and a product of tenacity by breaking elongation of said filament being smaller than 100. 

2. An improved crimped synthetic filament according to claim 1, further characterized by said cross-sectional profile being defined by the following equation; 3.0 x/y 11.0 0.15 X/Y 0.60 wherein x 32 Sum of length of branches of said cross-sectional profile of said filament y Average width of said branches of said cross section of said filament X Cross section area of said filament Y Area of a smallest circumscribed circle of said cross section of said filament.
 3. An improved crimed synthetic filament according to claim 1, further characterized by a minimum value of a moment of inertia of area of said cross section of said filament being more than 1.5 times larger than that of an imaginary circle having the same area and a product of tenacity by breaking elongation of said filament being smaller than
 100. 4. An improved crimped synthetic filament according to claim 1, wherein said filament is composed of poly- epsilon -caproamide polymer. 5 An improved crimped synthetic filament according to claim 2, wherein said filament is composed of poly- epsilon -caproamide polymer.
 6. An improved crimped synthetic filament according to claim 3, wherein said filament is composed of poly- epsilon -caproamide polymer. 